LVDS47/48EVK National Semiconductor, LVDS47/48EVK Datasheet - Page 10

• Manufacturer Part Number: LVDS47/48EVK
• Description: EVALUATION BOARD FOR LVDS47/48
• Manufacturer: National Semiconductor

Specifications of LVDS47/48EVK

• Main Purpose: Interface, Digital Cable Driver
• Utilized Ic / Part: DS90LV047A, DS90LV048A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Other names: *LVDS47/48EVK; *LVDS47/48EVK/NOPB; LVDS47/48EVK/NOPB

Figure 9: LVDS Channel #2 Waveforms - differential and calculated differential from single-ended waveform
LVDS waveforms may also be measured with high impedance probes such as common SD14 probe heads. These probes
offer 100k Ohm, 0.4 pF loading and a bandwidth of 4 GHz. These probes connect to a TEK 11801B scope (50 GHz
bandwidth). Probes with standard 50 Ohm loading should not be used on LVDS lines since they will load them too
heavily. 50 Ohm probes may be used on the receiver output signal in conjunction with the 453 Ohm series resistor
option (see option section below). Note that the scope waveform is an attenuated signal (50 Ohm/(450 Ohm + 50 Ohm)
or 1/10) of the output signal and the receiver output is loaded with 500 Ohm to ground.
6.1.7 Demo PCB Options
Option 1: 453 Ohm Resistors
A provision for a series 453 Ohm resistor (RS1, RS2, RS3 and RS4) is provided on the receiver output signal. By
cutting the trace between the “RS” pads and installing a 453 Ohm resistor a standard 50 Ohm scope probe may be used
(500 Ohm total load). Note that the signal is divided down (1/10) at the scope input.
Option 2: Disabling the LVDS Driver
The quad driver features a ganged enable. An active high or an active low input are provided. On the evaluation PCB,
the active low input (EN*) is routed to ground. The active high input (EN) is routed to a jumper (J3). The jumper
provides a connection to the V
plane (“ON”) or to the Ground plane (“OFF”). To enable the driver, connect the
CC
jumper to the power plane, to disable the driver connect the jumper to the ground.